EP3239260B1 - Use of adhesive substances for sticking together flexible printing plates - Google Patents

Description

The invention relates to the use of a pressure-sensitive adhesive comprising at least 60% by weight of a polymer blend, wherein the polymer blend consists of a first polyacrylate-based polymer component A and at least one second polyacrylate-based polymer component B and at least x% by weight of the first polymer component A Polymer blend is present, wherein 90 ≦ x ≦ 99, and wherein the second polymer component B and optionally present further polymer components in total to y wt .-% in the polymer blend are present, where y = 100 - x, for bonding printing plates on particular curved surfaces.

In the printing industry, various methods are known to transfer motifs by means of printing templates on, for example, paper or film. One possibility is the so-called flexographic printing.

In the flexographic printing process, flexible printing plates (also called clichés) are glued to printing cylinders or printing sleeves (the latter also referred to as sleeves). Such clichés consist for example of a polyethylene terephthalate film (PET film), to which a layer of a photopolymer is applied, in which by exposure of the printing and subsequent washing of the non-printing elements, the corresponding printing relief can be introduced. The gluing of the plate on the printing cylinder or the printing sleeve then takes place via the PET film. For bonding usually double-sided pressure-sensitive adhesive tapes are used, are placed on the very high demands. For the printing process, the pressure-sensitive adhesive tape must have a certain hardness but also a certain elasticity. These properties must be set very precisely, so that the generated print image according to the requirements provides the desired result. High demands are also placed on the pressure-sensitive adhesive, since the adhesive power should also be sufficient for it to be the pressure plate does not detach from the double-sided pressure-sensitive adhesive tape or the pressure-sensitive adhesive tape from the cylinder or the sleeve. This also applies at elevated temperatures - for example from 40 to 60 ° C - and at higher printing speeds, as well as at lower temperatures than room temperature - such as 15 ° C. In addition to this property, the PSA must also have reversible adhesive properties in order to be able to detach the printing plates after the printing processes (in this case, both the adhesive bond of the pressure-sensitive adhesive tape to the printing cylinder or to the printing sleeve and to the plate must be left without residue in order to reuse both Ensure components). This detachability should also be given after a bonding over a longer period of time (such as up to 6 months). In addition, it is desirable that the pressure-sensitive adhesive tape and in particular the printing plate can be removed without destroying it, as well as without much effort, since the printing plates are generally used several times. In addition, no residues should remain on the pressure plate and on the cylinder or the sleeve. In summary, very high demands are placed on the double-sided pressure-sensitive adhesive tapes suitable for this application.

The residue-free redetachability is a problem, especially in polar substrates such as steel, since it has been found here that the bond strengths increase significantly over time. In the context of this document, the terms "polar" and "high energy", ie with a high surface energy (OFE), are set equal with regard to surfaces, likewise the terms "nonpolar" and "low energy", since this simplifying model prevails in practice Behind this is the recognition that polar dipole forces are comparatively strong compared to so-called "disperse" or nonpolar interactions that are built without the involvement of permanent molecular dipoles.The basis of this model of interfacial energy and interfacial interactions is the notion that polar components interact only with polar ones and apolar only with apolar.

This energy and its components are often measured by measuring the static contact angles of different test liquids. The surface tensions of these liquids are assigned polar and non-polar components. From the observed contact angles of the droplets on the test surface, the polar and nonpolar portions of the surface energy of the test surface are determined. This can for example after the WKR model. An industrially customary alternative method is the determination by means of test inks according to DIN ISO 8296.

Suitable PSAs are, for example, those based on natural rubber, such as EP 760 389 A documented. However, pressure-sensitive adhesive tapes which have polyacrylate-based pressure-sensitive adhesives are also used for the stated purpose. For example, describes the WO 03/057497 A an acrylic PSA based on block copolymer for the stated application. The WO 2004/067661 A discloses a pressure sensitive adhesive tape having a soft acrylic monomer (T _G <-20 ° C) pressure-sensitive adhesive of at least 49.5% by weight of a hard, cyclic, or linear (meth) acrylic ester monomer (T _G > 30 ° C) and at least 10 wt .-% functionalized hard (meth) acrylic acid / ester monomers (T _G > 30 ° C), wherein the PSA is prepared in a two-stage process.

Another disadvantage of many known from the prior art pressure-sensitive adhesives for the bonding of printing plates is particularly evident when the glued clichés are to be cleaned of the ink. This is usually done by using solvents - for example those which also serve as solvents for the colors themselves - to wash off and remove the colors from the clichés. Here, larger amounts of solvent are often used, which aggravates the problem. This inevitably leads to a creeping of solvent under the edges of the bonding of the cliché on the pressure-sensitive adhesive tape and the edges of the adhesive tape on the printing cylinder or the printing sleeve. This can lead to a detachment of the bond (of the cliché on the tape or the adhesive tape on the cylinder or the sleeve), since the adhesives of the pressure-sensitive adhesive tape lose the necessary adhesion. The raised edges ("flags") resulting from this lack of solvent resistance are then also printed in the process, resulting in a faulty print image (generally referred to as "misprint"), unless it even causes mechanical problems with the banners in the printing apparatus and thus system failures comes. In practice, therefore, the adhesions of printing plates which have been mounted with adhesives of the prior art can be advantageously protected against the solvent by sealing the respective edges with single-sided pressure-sensitive adhesive tapes or with liquid or hot melt adhesives.

This additional sealing process means a significant additional effort and there is the danger of damaging the expensive printing plates, especially when using liquid or hot melt adhesives during disassembly.

The EP 2 226 372 A1 discloses an acrylate-based pressure-sensitive adhesive for the bonding of printing plates to cylinders or sleeves, which has a high acrylic acid content between 8 and 15% by weight. Other monomers are linear and branched acrylic acid esters, which are present in a certain ratio to one another. With such an adhesive, the requirements regarding Kantenabhebeverhalten and solvent resistance are quite well met. However, pressure-sensitive adhesives with a high proportion of acrylic acid tend to coat frequently on polar substrates, such as steel, from the impression cylinder. Increasingly, plastic sleeves, especially those based on polyurethane, are also being used. The masses on the compression sleeve side must adhere to both steel and low-energy sleeve surfaces, which poses an additional challenge in the development process. This problem also arises with the adhesive of the EP 2 226 372 A1 Especially when you use them on the side of the tape, which is directed to the printing cylinder or to the printing sleeve. Therefore, the disassembly of such adhesives from such substrates is associated with problems; There are very high disassembly forces, and it can lead to breakage of the adhesive tape used, or residues remain on the substrate surface.

In order to offer a pressure-sensitive adhesive which, even under the influence of solvents, ensures a good and secure adhesion to flexographic printing materials, in particular PET (polyethylene terephthalate), but nevertheless also after very long periods of very polar substrates - such as, for example, the surfaces of printing cylinders from steel or the printing sleeves determined by polar plastic surfaces - again, the adhesive should preferably be particularly suitable for the secure bonding of printing plates and wherein for an adhesive tape with the PSA, the stability of the adhesive tape composite, in particular the secure anchoring of the PSA on foam carriers - how polyolefinic foams - should be guaranteed, reveals the WO2014 / 001096 A1 an acrylate-based pressure-sensitive adhesive which comprises 2 to 20% by weight of an N-alkyl-substituted acrylamide and 5 to 25% by weight of a (meth) acrylic ester having a linear alkyl radical having at least 12 C atoms and 0.5 to 5% by weight .-% of (meth) acrylic acid.

Although such PSAs have improved properties compared to the prior art, it has been found that the bonding of the printing plates with the per se reversibly adhesive PSAs are primed by impurities in the solvents with which the printing plates are cleaned after printing.

By "primers" in the field of adhesive tapes is usually understood that the bond strength to substrates can be increased by pretreatment of these substrates with suitable chemicals. In the present case, where the reversibility of the bonding plays an important role, this priming is undesirable in particular if it happens unintentionally due to impurities. In the present case, a "priming effect" is understood to mean that the adhesive strength of the PSA to the printing plates contaminated by the color residues in the solvents is significantly increased in comparison with printing plates cleaned with pure solvent.

The contaminants are from paint residues of the inks in the solvents used for cleaning, with even such small amounts of impurities, not even visible, being sufficient to cause this effect. In this way, significantly higher bond strengths over time than is desired for redetaching the plates. The printing plates can sometimes be removed only with great effort, whereby they can be damaged, making reusability of the plates impossible. To avoid this, the printer is forced to use fresh solvent and wipes for each cleaning operation. Apart from the fact that this means an increased expenditure of time and materials, this is hardly practicable in practice. Precisely because the existing contaminations are often not visible to the naked eye, there is no acceptance among users of changing solvents and cleaning cloths.

The object of the present invention is therefore the use of a pressure-sensitive adhesive which, in the bonding of printing plates, in particular on printing cylinders and / or printing sleeves, counteracts the undesired priming effect of the printing ink residues in the solvents with which the printing plates are cleaned and thus a so-called "ink resistance because it is insensitive to the influence of Printing ink residues in the cleaning solvent is. The adhesive strength of the PSA on such contaminated surfaces can be equated with a physical anchoring, the cause of which can be attributed to at least one binder contained in printing inks (also called film former). A commonly used in printing inks binder is, inter alia, cellulose nitrate (colloquially "nitrocellulose", in the context of this document, both terms are used synonymously), which can form an interaction with the PSA on the bonding surface and thus causing this primer effect known.

The object is achieved with the use of a pressure-sensitive adhesive for bonding printing plates on in particular curved surfaces which comprises at least 60% by weight of a polymer blend, the polymer blend comprising a first polymer component A, a second polymer component B and optionally one or more further polymer components ( C, D, ...), wherein the first polymer component A is at least x wt .-% in the polymer blend, wherein 90 ≤ x ≤ 99, and wherein the second polymer component B and the optionally present further polymer components C, D ,. .. in total to y% by weight in the polymer blend, where y = 100 - x, where each polymer component (A, B, C, ...) is attributable to at least 60% by weight of (meth) acrylic monomers, so that none of the polymer components (A, B, C, ...) at room temperature with one of the other polymer components (A, B, C, ...) is homogeneously miscible, so that a multi-phase system is present.

Such a multiphase embodiment of the PSA in which one of the components is present in a defined excess in the defined amount range substantially reduces the resistance of the PSA to the influence of the ink residues. This is manifested in the low amount of force required to detach a cliché from the cylinder or sleeve (due to surface ink residue, increased). In particular, the force required compared to the force required for detachment with the same PSA without the influence of the ink residue is only slightly, preferably only imperceptibly, in particular not increased.

• Gewährleistung einer guten und sicheren Verklebung auf im Flexodruck gängigen Material wie insbesondere auf PET (Polyethylenterephthalat), auch unter dem Einfluss von Lösungsmitteln
• Lösbarkeit auch nach längerer Zeit auch von sehr polaren Substraten wie beispielsweise den Oberflächen von Druckzylindern aus Stahl oder den Oberflächen von polaren Kunststoffoberflächen bestimmter Druckhülsen
• Eignung für das sichere Verkleben von Druckklischees; wobei für ein Klebeband mit der Haftklebemasse die Stabilität des Klebebandverbundes, insbesondere die sichere Verankerung der Haftklebemasse auf Schaumträgern ,wie polyolefinischen Schäumen, und/oder auf Folienträgern gewährleistet sein soll.

In addition to the above-mentioned requirement, the PSA to be used according to the invention should preferably also fulfill the customary requirements which exist in the bonding of printing plates as far as possible, in particular:

• Ensuring a good and secure bonding on commonly used in flexographic printing material such as PET (polyethylene terephthalate), even under the influence of solvents
• Solubility even after a long time even of very polar substrates such as the surfaces of printing cylinders made of steel or the surfaces of polar plastic surfaces of certain printing sleeves
• Suitability for the secure bonding of printing plates; wherein the stability of the adhesive tape composite, in particular the secure anchoring of the PSA to foam carriers, such as polyolefinic foams, and / or on film carriers should be ensured for an adhesive tape with the PSA.

This requirement profile is also well met by the PSA according to the invention.

For the purposes of this document, the polymer component is understood to be a single polymer or a mixture of polymers which are, however, homogeneously miscible with one another such that such a mixture forms a single homogeneous phase. The underlying polymers may be homopolymers (of a single monomer type) and / or copolymers (of more than one type of monomer).

The polymers of the polymer components in this document are those which are attributable to at least 60% by weight of (meth) acrylic monomers (for the meaning of this term, see below). The polymer components A and / or B can advantageously and independently of one another comprise exclusively or partially those polymers which are at least 80% by weight attributable to (meth) acrylic monomers; in a particular embodiment, pure acrylate systems are used for the polymer components A and / or B, ie those polymers which are exclusively due to (meth) acrylic monomers - ie to 100 wt .-%.

If further components C, D, etc. are present, pure acrylate systems can also be used here-regardless of the composition of components A and B, but especially if these are too.

As used, the term "pressure-sensitive adhesives" (PSA) is understood as meaning those viscoelastic, polymeric masses which, if appropriate by appropriate addition with other components, such as, for example, tackifier resins, are used at the temperature of use (unless otherwise defined). at room temperature, ie 23 ° C) permanently tacky and permanently tacky and adhere to a variety of surfaces in contact, especially immediately adhere (have a so-called "tack" [also known as stickiness or Anfassklebrigkeit]). They are able, even at the application temperature without activation by solvents or heat - if necessary, under the influence of a more or less high pressure - sufficient to wet a substrate to be bonded so that between the mass and the substrate for the adhesion sufficient interactions can train.

Pressure-sensitive adhesives usually consist of a polymer component, also referred to as a base polymer component, which may be a homopolymer, a copolymer or a mixture of polymers (homopolymers and / or copolymers), and optionally additives (co-components, additives), in some cases to a considerable extent. The terms "polymer (component) based on specific monomers", "polymer (component) based on a monomer mixture" or "polymer attributable to particular monomers or polymer component to be recycled" mean, as is generally customary, that the polymer - or the polymers of the polymer component - can be obtained by - especially free radical - polymerization of the corresponding monomers or the corresponding monomer mixture.

Pressure-sensitive adhesives can in principle be produced on the basis of polymers of different chemical nature. The pressure-sensitive adhesive properties are influenced inter alia by the nature and the proportions of the monomers used - ie the composition of the monomer mixture - in the polymerization of the polymers on which the PSA is based, average molecular weight and molecular weight distribution of the polymers and by optional admixture of additives (type and amount) ,

To achieve the viscoelastic properties, the monomers on which the PSA-based polymers are based, and optionally existing additional components of the PSA in particular chosen so that the PSA have a glass transition temperature T _G below the application temperature (ie usually below room temperature). Below the glass transition temperature T _G PSAs behave brittle elastic (glassy-amorphous or partially crystalline); No sticky behavior can be formed here. Above the glass transition temperature T _G, the masses soften more or less strongly with increasing temperature, depending on the composition, and assume the viscosity values suitable for the pressure-sensitive adhesive properties in a certain temperature range before they become too thin at even higher temperatures in order to retain tack-adhesive properties. unless they decompose before).

Glass transition temperatures are reported as the result of measurements by differential scanning calorimetry DDK according to DIN 53 765; in particular Sections 7.1 and 8.1, but with uniform heating and cooling rates of 10 K / min in all heating and cooling steps (see DIN 53 765, Section 7.1, Note 1). The sample weight is 20 mg. A pretreatment of the PSA is carried out (see Section 7.1, first run). Temperature limits: - 140 ° C (instead of T _G - 50 ° C) / + 200 ° C (instead of T _G + 50 ° C). The specified glass transition temperature T _G is the sample temperature in the heating operation of the second run, at which half of the change in specific heat capacity is reached.

The specification of the glass transition temperatures as a characteristic of the monomers used is based on their respective homopolymer which is obtainable according to the synthetic prescription for acrylate PSAs in the experimental part, wherein instead of the monomer 400 g of the respective monomers were used. T _G is determined after removal of the solvent in the uncrosslinked state (in the absence of crosslinking agents).

In particular, the PSA to be used according to the invention is present in phase-separated form, so that the PSA to be used according to the invention is present at least microscopically and at least at room temperature, defined as 23 ° C., preferably in at least two-phase, optionally in multiphase morphology. so that at least two or more stable phases form, each of which is homogeneously homogeneous.

The polymer components contained in the pressure-sensitive adhesive are preferably chosen so that they are not miscible to homogeneity at 23 ° C. Particularly preferably, the polymer components are not homogeneously miscible with one another, at least in a temperature range from 0 ° C. to 50 ° C., in particular from -30 ° C. to 80 ° C., so that the pressure-sensitive adhesive is at least microscopically at least two-phase in these temperature ranges.

For the purposes of this specification, components are defined as "not homogeneously miscible with one another", even if the formation of at least two stable phases can be detected physically and / or chemically, at least microscopically, with one phase rich in one component and the second Phase is rich in the other component. The presence of negligible amounts of one component in the other, which does not preclude the formation of multiphase, is considered to be irrelevant. Thus, for example, small amounts of the second polymer component B may be present in the phase of the first polymer component A, provided that they are not essential amounts which influence the phase separation, the same applies to small amounts of the polymer component A in the polymer component B and in each case for the others the PSA polymer components present.

The phase separation may in particular be realized in such a way that discrete regions ("domains") that are rich in one of the polymer components-such as the first polymer component A-are formed substantially from the corresponding polymer component-in a continuous matrix that is rich at another Polymerkomnponente - such as the second polymer component B - is, that is formed essentially of the polymer component B -, is present. If further polymer components C, D,... Are present in the PSAs, in a particularly preferred embodiment of the invention they are likewise present as discrete regions ("domains") in the matrix formed by the polymer component A, independently of the Domains of the polymer component B and regardless of domains of optionally further existing polymer components, so that a multi-phase with more than two phases - namely in the number of not homogeneously miscible components - is present ..
A suitable analysis system for a phase separation is, for example, scanning electron microscopy. However, phase separation can also be achieved, for example show that the different phases have two independent glass transition temperatures in differential scanning calorimetry (DDK, DSC). Phase separation according to the invention is present if it can be clearly demonstrated by at least one of the analytical methods.

A phase separation between two polymer components can be realized particularly advantageously if the Hansen solubility parameters of the polymer components differ sufficiently from each other, expressed by the difference "Z". It has been found that the PSAs in this case are particularly ink-resistant.

δ_d, δ_p und δ_H können für Polyacrylate experimentell nicht direkt bestimmt, wohl aber über Inkrementsysteme berechnet werden. Eine gängige - auch in dieser Schrift angewendete - Methode ist die nach Stefanis/Panayiotou ( Prediction of Hansen Solubility Parameters with a New Group-Contribution Method; Int. J. Thermophys. (2008) 29:568-585; Emmanuel Stefanis, Costas Panayiotou ):
Zur Bestimmung der Hansen-Löslichkeitsparameter für die Polyacrylate werden die Löslichkeitsparameter der auf die einzelnen monomere zurückzuführenden Bausteine in den Polymeren, also die der Wiederholungseinheit in einer Polymerkette (ohne die polymerisierbare Doppelbindung, stattdessen eine kovalente sigma-Bindung wie sie in der Polymerkette vorliegt) gemäß der Vorschrift in der genannten Schrift berechnet. Dabei ist für jede Gruppe in dem Baustein jeweils ein bestimmter Wert für den dispersen Anteil (δ_D), den polaren Wechselwirkungen (δ_P) und den Wasserstoffbrückenbildungs-Anteil (δ_H) tabelliert, siehe Prediction of Hansen Solubility Parameters with a New Group-Contribution Method; Int. J. Thermophys. (2008), Tables 3 bis 6, Seiten 578 bis 582 .A description of solubility parameters known in the literature is made by using the one-dimensional Hildebrand parameter (δ). However, these one-dimensional δ values are subject to errors that are usually large in polar compounds such as acrylates or those capable of undergoing hydrogen bonding, such as acrylic acid. Because the model of the one-dimensional Hildebrand solubility parameter has only limited application, it has been further developed by Hansen ( Hansen Solubility Parameters: A User's Handbook, Second Edition; Charles M. Hansen; 2007 CRC Press; ISBN 9780849372483 ).
The Hansen solubility parameters widely used nowadays are three-dimensional solubility parameters. They consist of a disperse fraction (δ _D ), a fraction of polar interactions (δ _P ) and a contribution to the hydrogen bonds (δ _H ). With the Hildebrand parameter δ they are connected as follows: $${\mathrm{<figure-callout\; id="2"\; label="\delta "\; filenames="imgf0001.png"\; state="\{\{state\}\}">\delta </figure-callout>}}^2={\mathrm{<figure-callout\; id="2"\; label="\delta \; d"\; filenames="imgf0001.png"\; state="\{\{state\}\}">\delta \; </figure-callout>}}_d^{}+{\delta }_{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="imgf0001.png"\; state="\{\{state\}\}">p</figure-callout>}}^2+{\delta }_{\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="imgf0001.png"\; state="\{\{state\}\}">H</figure-callout>}}^2$$

δ _d , δ _p and δ _H can not be determined experimentally for polyacrylates, but can be calculated by increment systems. A common - also used in this writing - method is the after Stefanis / Panayiotou ( Prediction of Hansen Solubility Parameters with a New Group Contribution Method; Int. J. Thermophys. (2008) 29: 568-585; Emmanuel Stefanis, Costas Panayiotou ):
In order to determine the Hansen solubility parameters for the polyacrylates, the solubility parameters of the components attributable to the individual monomers in the polymers, ie the repeating unit in a polymer chain (without the polymerizable double bond, instead a covalent sigma bond as described in US Pat Polymer chain is present) calculated according to the rule in the cited document. In each case a specific value for the disperse fraction (δ _D ), the polar interactions (δ _P ) and the hydrogen bond formation fraction (δ _H ) is tabulated for each group in the building block, see Prediction of Hansen Solubility Parameters with a New Group Contribution Method; Int. J. Thermophys. (2008), Tables 3 to 6, pages 578 to 582 ,

Examples:

Polyacrylic acid contains the repeating unit

- [- CH ₂ -CHCOOH-] _n -;

according to the increment system of Stefanis / Panayiotou, the Hansen solubility parameters (a CH ₂ group, a CH group and a COOH group) for the corresponding building block are δ _d = 17.7, δ _p = 8.6 and δ _H = 11.1. Polybutyl acrylate contains the repeating unit

- [- CH ₂ -CHCOO (CH ₂ ) ₃ CH ₃ -] _n -;

with four CH ₂ groups, a CH group, a COO group and a CH ₃ group, the Hansen solubility parameters for the corresponding building block are δ _d = 17.1, δ _p = 8.6 and δ _H = 6 ; 5.

After the Hansen solubility parameter of the monomer building blocks has been calculated, it is possible to determine the corresponding Hansen solubility parameters of the polyacrylates (copolymers). The solubility parameters (δ _D , δ _P , δ _H ) for acrylate copolymers are determined from the molar fraction of the individual monomers (building blocks) of which the polyacrylate is composed, the respective values being based on the molar fraction of the monomer building block in the copolymer is multiplied and then the proportional parameters (δ _d , δ _p , δ _H for each monomer) are summed.

The example of a polyacrylate consisting of 97 wt .-% butyl acrylates and 3 wt .-% acrylic acid, which corresponds to a molar composition of 84.8 mol% butyl acrylate and 5.2 mol% acrylic acid, this is illustrated. δ _d δ _p δ _H Butyl acrylate (δ _d = 17.1, δ _p = 8.6 and δ _H = 6.5) 0.848 x 17.1 = 16.2 0.848 x 8.6 = 8.2 0.848 x 6.5 = 6.1 Acrylic acid (δ _d ) = 17.7, δ _p = 8.6 and δ _H = 11.1) 0.052 x 17.7 = 0.9 0.052 x 8.6 = 0.4 0.052 x 11.1 = 0.6 + polyacrylate 17.1 8.6 6.7

The following procedure is followed for homogeneously miscible polymer mixtures: The Hansen solubility parameters of a respective polymer are multiplied in each case by the molar fraction of this polymer in the polymer component and the proportional values are then added in order to arrive at the respective parameter of the polymer component.

The difference between two polymer components 1 and 2 (for example, polymer components A and B) is given in this document by the parameter Z. The parameters δ _d1 , δ _p1 and δ _H1 of polymer component 1 are each subtracted from the corresponding parameters δ _d2 , δ _p2 and δ _{H2 of} the polymer component 2. The absolute value is determined from the respective difference value and this is added up in each case to the total factor Z: $$\mathrm{Z}=\left|{\mathrm{\delta }}_{\mathrm{d}1}-{\mathrm{<figure-callout\; id="2"\; label="\delta \; d"\; filenames="imgf0001.png"\; state="\{\{state\}\}">\delta \; </figure-callout>}}_{\mathrm{d}}\right|+\left|{\mathrm{\delta }}_{\mathrm{p}1}-{\mathrm{<figure-callout\; id="1"\; label="\delta \; p"\; filenames="imgf0001.png"\; state="\{\{state\}\}">\delta \; </figure-callout>}}_{\mathrm{p}}\right|+\left|{\mathrm{\delta }}_{\mathrm{H}1}-{\mathrm{<figure-callout\; id="2"\; label="\delta \; H"\; filenames="imgf0001.png"\; state="\{\{state\}\}">\delta \; </figure-callout>}}_{\mathrm{H}}\right|$$

For a number of very suitable monomers, the respective Hansen solubility parameters are listed in the appended Table 3, so that the above values for polymer components with polymers formed therefrom are easy to determine.

Particularly preferred pressure-sensitive adhesives to be used according to the invention are characterized in that the differences Z of all components in each case assume more than the value 1 in each case.

A further aspect of the invention therefore relates to a pressure-sensitive adhesive to be used which comprises at least 60% by weight (based on the PSA) of a polymer blend, initially independently of the phase separation problem, wherein the polymer blend comprises a first polymer component A, a second polymer component B and optionally one or more further polymer components (C, D, ...), wherein the first polymer component A is at least x wt .-% (based on the polymer blend) in the polymer blend, wherein 90 ≤ x ≤ 99, and wherein the second polymer component B and the optional further polymer components C, D,... present in total in the amount of y% by weight (based on the polymer blend) in the polymer blend, where y = 100 - x, where each polymer component (A, B, C, ...) is attributable to at least 60% by weight of (meth) acrylic monomers, and where the difference Z of the Hansen solubility parameters of each of the polymer components A, B, C, ... with each of the other polymer components A, B, C ... at least the value 1 assumes.

As a result of the chosen differences, it is particularly preferable for none of the polymer components (A, B, C,...) To be homogeneously miscible at room temperature with one of the other polymer components (A, B, C, Multiphase system is present.

Detailed description of the invention Composition of the polymer blend

The pressure-sensitive adhesive to be used according to the invention contains a polymer blend having at least two polymer components - namely a first polymer component A and a second polymer component B - which are each obtainable from one or more polymers by conventionally known polymerization processes, such as free radical polymerization or controlled free radical polymerization. In principle, the monomers for preparing the polymers of components A and B - as well as any further polymer components C, D,... Present - can be chosen from the same monomer pool, with the proviso that the selection is made such that the components do not react at room temperature are homogeneously miscible with each other.

The polymers of the polymer components A, B, C,... Are in particular those polyacrylate-based polymers, ie those polymers which are at least predominantly-in particular more than 60% by weight-on acrylic acid esters and / or methacrylic acid esters, and optionally their free acids , as monomers (hereinafter referred to as "acrylic monomers") are attributed. Polyacrylates are preferably obtainable by free radical polymerization. Polyacrylates may optionally contain further building blocks based on further, non-acrylic copolymerizable monomer.

The polyacrylates may be homopolymers and / or especially copolymers. The term "copolymer" for the purposes of this invention comprises both copolymers in which the comonomers used in the polymerization are purely randomly incorporated, as well as those in which gradients in the comonomer composition and / or local enrichments of individual Comonomer types as well as whole blocks of a monomer in the polymer chains occur. Also alternating comonomer sequences are conceivable.

The polyacrylates may be, for example, of linear, branched, star or grafted structure, and may be homopolymers or copolymers. Advantageously, the average molecular weight (weight average M _W ) of at least one of the polyacrylates of the polyacrylate base polymer, with several polyacrylates present advantageously the majority of the weight of the polyacrylates, in particular all existing polyacrylates in the range of 250 000 g / mol to 10 000 000 g / mol, preferably in the range of 500,000 g / mol to 5,000,000 g / mol.

Particularly preferably, the composition of the polyacrylate component is chosen such that the polyacrylate component has a glass transition temperature (DDK, see below) of not more than 0 ° C., preferably not more than -20 ° C., very preferably not more than 40 ° C has.

ein geeigneter Glasübergangspunkt T_G für das Polymer ergibt; mit
n = Laufzahl über die eingesetzten Monomere, w_n = Massenanteil des jeweiligen Monomers n (Gew.-%) und T_G,n = jeweilige Glasübergangstemperatur des Homopolymers aus den jeweiligen Monomeren n in K. Glasübergangstemperaturen von Homopolymeren können bis zu einer bestimmten oberen Grenzmolmasse von der Molmasse des Homopolymeren abhängen; die Bezugnahme auf Glasübergangstemperaturen von Homopolymeren in dieser Schrift erfolgt in Bezug auf solche Polymere, deren Molmassen oberhalb dieser Grenzmolmasse liegen, also im Glasübergangstemperatur-konstanten Bereich. Bestimmung des T_G erfolgt nach Entfernung des Lösemittels im unvernetzten Zustand (in Abwesenheit von Vernetzern).The glass transition temperature of copolymers can be selected by selecting and quantitative composition of the components used advantageously such that in analogy to the Fox equation according to equation G1 $$\frac{1}{{\mathrm{T}}_{\mathrm{G}}}={\displaystyle \underset{\mathrm{n}}{\Sigma }\frac{{\mathrm{w}}_{\mathrm{n}}}{{\mathrm{T}}_{\mathrm{G}.\mathrm{n}}}}$$

gives a suitable glass transition point T _G for the polymer; With
n = number of runs over the monomers used, w _n = mass fraction of the respective monomer n (wt .-%) and T _{G, n} = respective glass transition temperature of the homopolymer of the respective monomers n in K. glass transition temperatures of homopolymers can up to a certain upper limit molecular weight depend on the molecular weight of the homopolymer; the reference to glass transition temperatures of homopolymers in this document is in relation to those polymers whose molecular weights are above this Grenzmolmasse, ie in the glass transition temperature constant range. T _G is determined after removal of the solvent in the uncrosslinked state (in the absence of crosslinking agents).

Similarly, equation G1 can also be used to determine and predict the glass transition temperature of polymer blends. Then, as far as homogeneous mixtures are concerned,
n = number of runs over the polymers used, w _n = mass fraction of the respective polymer n (wt .-%) and T _{G, n} = respective glass transition temperature of the polymer n in K. Blending with adhesive resins usually increases the static glass transition temperature.

Particularly advantageous statistical copolymers can be used.

At least one type of polymer of the polyacrylate component is advantageously based on unfunctionalized α, β-unsaturated esters. If these are used for the at least one polymer in the polyacrylate component having a copolymer character, all the compounds known to the person skilled in the art which are suitable for the synthesis of (meth) acrylate (co) polymers can be used as monomers in the preparation of this at least one polymer type , Preference is given to α, β-unsaturated alkyl esters of the general structure

CH ₂ = C (R ¹ ) (COOR ² ) (I)

wherein R ¹ = H or CH ₃ and R ² = H or linear, branched or cyclic, saturated or unsaturated alkyl radicals having 1 to 30, in particular having 4 to 18 carbon atoms.

At least one kind of monomers for the polyacrylates of the polyacrylate component of the advantageous adhesive to be used according to the invention are those whose homopolymer has a glass transition temperature T _G of not more than 0 ° C., very preferably at most -20 ° C. These are in particular esters of acrylic acid with linear alcohols having up to 10 C atoms or branched alcohols having at least 4 C atoms and esters of methacrylic acid with linear alcohols having 8 to 10 C atoms or branched alcohols having at least 10 C atoms. Furthermore, it is additionally possible to use monomers whose homopolymer has a glass transition temperature T _G of more than 0 ° C. As specific examples, one or more members are preferably selected from the group comprising
Methylacrylate, methylmethacrylate, ethylacrylate, n-propylacrylate, n-butylacrylate, n-butylmethacrylate, n-pentylacrylate, n-hexylacrylate, n-heptylacrylate, n-octylacrylate, n-octylmethacrylate, n-nonylacrylate, n-nonylmethacrylate, n-decylacrylate, n-decyl methacrylate, isobutyl acrylate, isopentyl acrylate, isooctyl acrylate, isooctyl methacrylate, the branched isomers of the aforementioned compounds, such as 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, 2-propylheptyl acrylate.

Furthermore, monomers can be chosen which tend to form part-crystalline regions in the polymer. This behavior is noted for acrylic esters and Methacrylic acid esters having a linear alkyl radical having at least 12 carbon atoms in the alcohol radical, preferably of at least 14 carbon atoms in the alcohol radical. According to the invention, stearyl acrylate and / or stearyl methacrylate can be used particularly advantageously here, for example.

Further advantageously usable monomers are monofunctional acrylates and / or methacrylates of bridged cycloalkyl alcohols having at least 6 C atoms in the cycloalkyl alcohol radical. The cycloalkyl alcohols may also be substituted, for example by C ₁ - to C ₆ -alkyl groups, halogen atoms or cyano groups. Specific examples are cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate and 3,5-dimethyl adamantyl acrylate.

For varying the glass transition temperature, it is also possible to use for the production of the polyacrylates a proportion of such comonomers whose homopolymers have a high static glass transition temperature. Suitable components are aromatic vinyl compounds, such as, for example, styrene, where the aromatic nuclei preferably comprise C ₄ to C _{18 building} blocks and may also contain heteroatoms. Particularly preferable examples are 4-vinylpyridine, N-vinylphthalimide, methylstyrene, 3,4-dimethoxystyrene, 4-vinylbenzoic acid, benzylacrylate, benzylmethacrylate, phenylacrylate, phenylmethacrylate, t-butylphenylacrylate, t-butylphenylmethacrylate, 4-biphenylacrylate and methacrylate, 2-naphthylacrylate and methacrylate and mixtures of those monomers, this list is not exhaustive.

As comonomers for the acrylic monomers it is also possible to use further monomers copolymerizable with acrylic monomers, for example in an amount of up to 40% by weight. Such comonomers may, in principle, be all acrylate-compatible compounds having copolymerizable double bonds, such as vinyl compounds. Such vinyl compounds may be wholly or partly selected from the group comprising vinyl esters, vinyl ethers, vinyl halides, vinylidene halides, vinyl compounds having aromatic rings and heterocycles, in particular in the α-position to the double bond. Particularly suitable comonomers are, for example, vinyl acetate, vinyl formamide, vinyl pyridine, ethyl vinyl ether, vinyl chloride, vinylidene chloride, acrylonitrile.

But other copolymerizable with acrylic monomers compounds can be used here.

For effective crosslinking, it is particularly advantageous if at least some of the polyacrylates have functional groups with which the crosslinkers used according to the invention can react. For this purpose, monomers are preferred Acid groups used, such as acrylic acid, sulfonic acid or phosphonic acid groups, or with acid anhydride.

Particularly preferred examples of monomers for polyacrylates are acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, aconitic acid, dimethylacrylic acid, β-acryloyloxypropionic acid, trichloroacrylic acid, vinylacetic acid, vinylphosphonic acid, maleic anhydride.

Networking

Another criterion for the suitability as a pressure-sensitive adhesive is cohesion. Usually, the polymer composition must have sufficient cohesion in order to be able to impart adhesion during the bonding and not to flow out of the adhesive bond. By means of suitable cohesion-increasing measures, such as crosslinking reactions (formation of bridge-forming linkages between the macromolecules), the temperature range in which a polymer composition has adhesive properties can be set, increased and / or shifted. The scope of the PSAs can thus be optimized by adjusting the flowability and cohesion of the mass.

Particularly preferably, the procedure is such that at least the matrix component-in particular formed by the first polymer component A-is crosslinked. The domains of the other polymer components-in particular of the second polymer component B, optionally also of any other polymer components present-can likewise be crosslinked, but also uncrosslinked, in each case independently of the crosslinking state of the other polymer components present.

In order to obtain the optimum properties of the PSA to be used according to the invention, it should very preferably be crosslinked. As already shown above, it is advantageous if at least the matrix polymer component is crosslinked, but alternatively or additionally, the other (present as domains) polymer components can be crosslinked, in each case independently of the optional further polymer components.

The PSA to be used according to the invention is suitable for use in the bonding of printing plates to printing cylinders and sleeves, in particular as an adhesive layer an adhesive tape on the side facing the printing cylinder or the sleeve (ie in contact with these substrates in contact with the adhesive), particularly suitable if their micro-shear path - with respect to the shear in 15 min at 40 ° C an initial 13 mm x 10 mm large area of the coated PSA having a thickness corresponding to a basis weight of 50 g / m ² , when loaded with 1.0 N in the direction of greater length expansion according to method F - between 100 .mu.m and 300 .mu.m. The best properties of the adhesive according to the invention to be used in a cross-linked state, which corresponds to a micro-shear path with respect to the reference above between 125 microns and 250 microns.

The abovementioned values can be readily adjusted by using a suitable crosslinker in a well-defined amount, in particular in the case of an almost complete crosslinking reaction.

By adding suitable thermal crosslinkers, the PSA to be used in accordance with the invention is advantageously thermally crosslinkable, so that it is possible to dispense with the addition of actinically activatable crosslinkers, for example crosslinkers activatable by ultraviolet light (UV crosslinkers). The thermal crosslinking can be carried out under conditions which are considerably milder for the PSA, since the action of the rays, which also have a destructive effect, can be avoided.

However, if desired on a case-by-case basis, it is also possible to effect crosslinking exclusively or additionally by exposure to actinic radiation, with any necessary or promoting crosslinker substances being added (e.g., UV crosslinker).

In general, the PSA to be used according to the invention thus contains thermal crosslinkers, ie those substances which allow (initiate) and / or promote a crosslinking reaction under the influence of thermal energy.

The setting of the crosslinking state-in particular to the abovementioned preferred ranges-can be effected, for example, by the use of covalently reacting crosslinkers, in particular epoxides, isocyanates and / or aziridines, and / or by the use of coordinating crosslinkers, in particular metal chelates, preferably aluminum chelate.

Metal chelates, in particular aluminum chelates, for example in the form of aluminum (III) acetylacetonate, are preferably used in an amount of from 0.15 to 0.35 parts by weight, more preferably from 0.2 to 0, in order to achieve the above-mentioned crosslinking state. 3 parts by weight, in each case based on 100 parts by weight of the polymer component (solvent-free) used.

Further very suitable thermal crosslinkers are, for example, epoxides containing tertiary amine functions, in particular tetraglycidyl meta-xylenediamine (N, N, N ', N'-tetrakis (oxiranylmethyl) -1,3-benzenedimethanamine). These compounds are preferably used in an amount of 0.03 to 0.1 parts by weight, more preferably 0.04 to 0.07 parts by weight, for example, 0.06 parts by weight, again in each case based on 100 wt .) Parts of the polymer component (solvent-free) used to achieve the above-defined state of crosslinking.

Advantageously, crosslinking is carried out in such a way that the crosslinking reaction proceeds as completely as possible. For this purpose, it is favorable if at least 85% by weight, preferably at least 90% by weight, of the crosslinker are reacted during the crosslinking reaction. With a corresponding implementation of the crosslinking reaction, the above-defined crosslinking state of the PSA could be realized in each case.

The preparation of a crosslinked PSA is carried out in an advantageous procedure such that initially the polymers of the respective polymer components are prepared from the correspondingly based monomer mixtures by radical polymerizations. These polymer components are then intimately mixed. During or preferably after the polymerization, at least one thermal crosslinker, in particular one or more of the crosslinkers listed above, very particularly preferably aluminum (III) acetylacetonate or tetraglycidyl meta-xylenediamine added, in particular in the respective amounts indicated above. If - as shown below for the PSA of the invention but not usually required - further additives are to be added, they are also mixed.

The pressure-sensitive adhesive mixed with the crosslinker is crosslinked to such an extent by supplying thermal energy that its crosslinking state corresponds to a micro-shear path in the range from 100 μm to 300 μm, preferably in the range from 125 μm to 250 μm (see above for reference).

Advantageous embodiments of the invention

In a particularly preferred embodiment, the polymer blend is formed exclusively from the polymer components A and B, so that a two-phase system is present. The first polymer component A can be formed by a single polymer which may be a homopolymer, but also a copolymer, in particular polymerized from the monomers mentioned in this document.

Alternatively, the first polymer component A may be a homogeneous mixture of two or more polymers, that is, consist of a plurality of mutually miscible polymers which may each independently be homopolymers or copolymers. One, some or preferably all of these polymers are advantageously attributable to the monomers mentioned in this document.

The second polymer component B can be formed by a single polymer, which may be a homopolymer, but also a copolymer, in particular polymerized from the monomers mentioned in this document.

Alternatively, the second polymer component B may be a homogeneous mixture of two or more polymers, that is to say consist of a plurality of mutually miscible polymers which may each independently be homopolymers or copolymers. One, some or preferably all of these polymers are advantageously attributable to the monomers mentioned in this document.

In a particular embodiment, the first polymer component A and the second polymer component B are each formed by a single copolymer based on acrylate, which in particular are composed in such a way that they meet the specifications for the pressure-sensitive adhesive.

In a further particular embodiment, the first polymer component A is a homogeneous mixture of two or more acrylate-based copolymers, while the second polymer component B is formed by a single acrylate-based copolymer. The polymer components are especially composed in such a way that they meet the specifications for the pressure-sensitive adhesive.

The optional further polymer components C, D,... Can also be realized independently of each other by a single homo- or copolymer or by a homogeneous polymer mixture. The statements made above for the second polymer component B apply mutatis mutandis.

admixtures

In a preferred manner, the polymer component as such-without any significant proportions of other constituents-is tack-adhesive. The polymer blend constitutes at least 60% by weight of the PSA.

In a preferred procedure, the polymer blend constitutes at least 98% by weight, particularly preferably more than 99.9% by weight, of the composition of the PSA minus the crosslinker present (ie based on all constituents of the PSA, with the exception of the or the Crosslinker, since this is usually present and therefore should be disregarded for the consideration of the additive freedom). Very preferably, a value of 100% by weight is chosen (without prejudice to the presence of crosslinkers, as described immediately above).

Usually, however, pressure-sensitive adhesives comprise a small proportion of impurities, unreacted monomers or the like as a result of the preparation.

In an advantageous embodiment, the PSA to be used according to the invention is resin-free and / or, without prejudice to the presence or absence of crosslinkers (see above), free of other additives.

For fine adjustment of the pressure-sensitive adhesive properties or as contributing components to a crosslinking or curing reaction, pressure-sensitive adhesives are frequently mixed with resins (tackifying resins, reactive resins). Accordingly, the PSA to be used according to the invention can be realized in an outstanding manner without the admixture of resins, without this having a disadvantageous effect on its suitability for the stated intended use. Both tackifying, thermoplastic and reactive resins can be dispensed with. In particular, the absence of resins leads to a particularly residue-free substrate surface after disassembly of the adhesive tape, for example to particularly residue-free printing cylinders or printing sleeves, after the previously bonded pressure-sensitive adhesive tape according to the invention has been removed again.

As resins in the context of this document, in particular those oligomeric and (low) polymeric compounds are considered whose number average molecular weight M _{n is} not more than 5,000 g / mol. Of course, short-chain polymerization products which are formed in the polymerization of the above-defined monomer mixture for the preparation of the polymer component of the PSA to be used according to the invention are not subsumed under the term "resins".

Tackifying resins - also referred to as tackifier resins - often have softening points in the range of 80 to 150 ° C, without wishing to be limited to the definition of this range. The information on the softening point T _E of oligomeric and polymeric compounds, such as the resins, refer to the ring-ball method according to DIN EN 1427: 2007 with appropriate application of the provisions (investigation of Oligomer- or polymer sample instead of bitumen in otherwise maintained procedure). The measurements are carried out in the glycerol bath. Such resins which can be dispensed with in the case of the PSA according to the invention are, for example, natural and / or synthetic resins, such as pinene and indene resins, rosin and rosin derivatives (rosin esters, also rosin derivatives stabilized by, for example, disproportionation or hydrogenation), polyterpene resins, terpene-phenolic resins , Alkylphenol resins, aliphatic, aromatic and aliphatic-aromatic hydrocarbon resins, to name but a few.

Reactive resins are understood as meaning those resins which have functional groups in such a way that they could react under suitable activation to further constituents of the PSA-such as, for example, the macromolecules of the polymer components or other reactive resins.

If desired, however, it is also possible for the adhesives and / or reactive resins to be used according to the invention to be mixed in an alternative procedure.

In order to optimize the pressure-sensitive adhesive to be used according to the invention, it is additionally possible to add the additives known in each case to the person skilled in the art for the respective purpose. An advantage of the PSA to be used according to the invention, however, is, in particular, apart from the crosslinkers discussed separately, additive-free outstanding for the mentioned purpose to be suitable. The presence of further additives - without prejudice to the presence or absence of crosslinking agents - can thus be dispensed with without adversely affecting the advantageous properties of the PSA. Thus, in particular, the addition of additives such as plasticizers, fillers, functional additives to achieve certain physical properties (such as electrically conductive fillers, thermally conductive fillers and the like), flame retardants (such as ammonium polyphosphate and its derivatives) and the like can be dispensed with.

The adhesives to be used according to the invention are particularly suitable for the releasable attachment of flexible printing plates, since the printing plates with their help for a good and secure fix, on the other hand, the detachment is easily possible, even if the printing plates were cleaned with solvent through Printing ink residue is contaminated.

Process for the preparation

A further aspect relates to a first process for preparing a pressure-sensitive adhesive, wherein at least one second polymer component B and optionally one or more further polymer components (C, D,...) Are intimately mixed with a first polymer component A, so that a polymer blend is produced at least 60% by weight of the PSA, the first polymer component A being at least x% by weight in the polymer blend, where 90.ltoreq.x.ltoreq.99, the second polymer component B and the further polymer components C, D,. in total at y% by weight in the polymer blend, where y = 100 - x, wherein each polymer component (A, B, C, ...) is at least 60% by weight attributable to (meth) acrylic monomers, and wherein none of the polymer components (A, B, C, ...) at room temperature with one of the other polymer components (A, B, C, ...) is homogeneously miscible, so that a multi-phase system is formed.

Another method for producing a pressure-sensitive adhesive is characterized in that at least one second polymer component B and optionally one or more further polymer components (C, D,...) Are intimately mixed with a first polymer component A, so that a polymer blend is produced at least 60% by weight of the PSA, wherein the first polymer component A is at least x% by weight in the polymer blend, where 90 ≦ x ≦ 99, where the second polymer component is B and the optional further polymer components C, D,... present in total in the polymer blend in the amount of y% by weight, where y = 100 - x, where each polymer component (A, B, C, ...) contains at least 60% by weight .-% on (meth) acrylic monomers is due. In this process, each polymer component (A, B, C, ...) comprises such polymers, each obtained by polymerization of monomers, wherein the composition of the monomers for the polymers of each polymer component are selected such that the difference Z of the Hansen Solubility parameter of each of the polymer components A, B, C, ... with each of the other polymer components A, B, C ... more than the value 1 assumes.

The implementation of this method particularly preferably leads to such a pressure-sensitive adhesive in which none of the polymer components (A, B, C,...) Is homogeneously miscible at room temperature with one of the other polymer components (A, B, C,...) , so that a multi-phase system is created.

The abovementioned processes can be used outstandingly to prepare the pressure-sensitive adhesive to be used according to the invention in its basic forms or in its advantageous embodiments, as mentioned in the context of this document.

use

The invention relates to the use of a pressure-sensitive adhesive - including any of its embodiments
for gluing pressure plates
in particular curved surfaces.

The printing plate may advantageously be one made of a polyethylene terephthalate film, to which at least one layer of a photopolymer is applied.

The surface on which the printing plate is bonded, for example, consists of steel, polyurethane or a glass fiber-resin material.

The use of the invention relates in particular to the bonding of a printing plate on such surfaces, which are part of a printing cylinder or a Drucksleeves.

Particularly suitable is the pressure-sensitive adhesive - including each of its embodiments
for use in printing processes using celluslosenitrathaltigen inks, and there, as shown above, in particular for the bonding of printing plates on curved surfaces, such as on Drucksleeves or Druckzylinern ..

The PSA to be used according to the invention is suitable for secure bonding to common materials and is distinguished by good residue-free removability. This behavior shows them especially for very polar substrates, of which adhesives according to the prior art, especially after a prolonged Verklebungsdauer, regularly can not be solved without the retention of residues again.

A very good reversibility, so residue-free redetachability, could be found even for substrates whose surface energy is 45 mN / m or more, especially for materials with surface energies in the range of 48 mN / m or more, such as steel, according to the literature Value 50 mN / m.

The invention furthermore relates to the use of the PSA as adhesive layer for PSA tapes, in particular for double-sided adhesive PSA tapes and the corresponding pressure-sensitive adhesive tapes comprising a layer of PSA of the invention, and the corresponding adhesive tapes per se. Such adhesive tapes can in particular be equipped with a carrier, optionally further layers and two outer adhesive layers, which in turn temporarily - for better handling, storage and offering - on one or both PSA layers with a temporary cover material - also referred to as liners - may be provided. In the case of such double-sided pressure-sensitive adhesive tapes, both adhesive layers can be formed from the PSA of the invention - and in particular identical in composition and / or thickness and / or crosslinking state - or one of the adhesive layers can be realized by a PSA to be used according to the invention, while the other adhesive layer is selected from another PSA, which can be optimally matched to the corresponding substrate to be bonded. As Support materials for the pressure-sensitive adhesive tapes are the conventional and familiar to those skilled in films, such as polyester, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), biaxially oriented polypropylene (BOPP), monoaxially oriented polypropylene (MOPP), polyurethane ( PU), polyvinyl chloride (PVC) and so on, and these materials can also be used as a foamed layer, respectively. It is also possible to use composites composed of several layers, for example a film layer and a foam layer.

It should be noted that the PSA to be used according to the invention can also be used as an adhesive layer of other adhesive tapes, for example single-layer, strapless adhesive tapes ("transfer adhesive tapes"), which consist of the adhesive layer.

As described, the PSA to be used according to the invention can be used outstandingly for bonding flexible printing plates on curved surfaces, in particular for bonding printing plates or printing plates with printing sleeves or printing cylinders, in particular as an adhesive layer of a pressure-sensitive adhesive tape. The particular suitability of the PSA for reversible bonding on plastic (see above) to be used according to the invention makes it particularly suitable for bonding to printing plates or plates made from this material. Since the adhesive has good properties also on other materials, the corresponding pressure-sensitive adhesive tapes can be used very flexibly, even when used in flexographic printing. Thus, the pressure-sensitive adhesive of the invention can be used as the adhesive layer of double-sided pressure-sensitive adhesive tapes, the pressure-sensitive adhesive to be used according to the invention being the adhesive layer directed toward the printing plate or cliche during the bonding. In particular, double-sided pressure-sensitive adhesive tapes are used, as described above. As a carrier material, a foamed sheet is advantageously used, for example a polymer foam layer. Thus, in particular foamed polyolefins - such as polyethylene and polypropylene - use, particularly preferred is a polyethylene / ethylene vinyl acetate foam. Furthermore, by way of example foamed polyurethanes or foamed polyvinyl chlorides can be used. Generally, roughening or other pretreatment of the support material can be used to improve the pressure-sensitive adhesive anchorage. One way of roughening and chemically modifying the polymer structure is by wet-chemical etching of the support material. In addition to the Etching can also be pretreated in other ways. Thus, to improve the anchoring, the support materials can be physically and chemically pretreated. For physical treatment, the film is preferably treated with flame or corona or plasma. For the chemical pretreatment, the support material is provided with primer, wherein in a particularly preferred design reactive precursors are used. Suitable primer materials are, for example, reactive primers.

The construction of the adhesive tapes corresponds in very preferred embodiments of a layer sequence, as shown in the Fig. 1a and 1b are reproduced. In this case, the PSA of the invention is particularly preferably used in the sense of the adhesive layer 9, that is, the adhesive layer used in the application to the printing cylinder or to the printing sleeve, since it is optimized for this purpose.

Due to the wide range of uses of the PSA to be used according to the invention, it is also suitable for the adhesive layer which is in contact with the printing plate.

The adhesive tape is advantageously used for bonding a cliché, which is composed of a PET film 2 and a layer of a photopolymer 1. The layers 3 and 9 form the outer adhesive layers of a double-sided adhesive cliché adhesive tape, which is thanks to its carrier foam layer 8 compressible and elastic. In this case, the PSA to be used according to the invention can be used either for layer 3 or for layer 9, or particularly advantageously for both layers 3 and 9.

3

Haftklebemasse zur Verankerung des Klischees

4

die vorbehandelte - insbesondere geätzte oder coronabehandelte - obere Oberfläche der PET-Folie 5

5

Folie aus Polyethylenterephthalat (PET)

6

die vorbehandelte - insbesondere geätzte oder coronabehandelte - untere Oberfläche der PET-Folie 5

7

Klebemasse - insbesondere Haftklebemasse - zur Verankerung der Träger-Schaumschicht 8 auf der PET-Folie 5

8

Träger-Schaumschicht, z.B. Polyethylen/Ethylenvinylacetat-Schaum

9

Haftklebemasse zur Verankerung auf dem Druckzylinder

10

Polyethylen-Befilmung der Träger-Schaumschicht 8 (beidseitig)

In the FIGS. 1a and 1b mean:

3

Pressure-sensitive adhesive for anchoring the cliché

4

the pretreated - in particular etched or corona-treated - upper surface of the PET film 5

5

Polyethylene terephthalate (PET) film

6

the pretreated - in particular etched or corona treated - lower surface of the PET film 5

7

Adhesive - in particular pressure-sensitive adhesive - for anchoring the carrier foam layer 8 on the PET film 5

8th

Carrier foam layer, eg polyethylene / ethylene vinyl acetate foam

9

Pressure-sensitive adhesive for anchoring on the printing cylinder

10

Polyethylene coating of carrier foam layer 8 (both sides)

Especially in the printing industry, it is important that the adhesive tapes used here have a high degree of flexibility, that is to say that they can change their thickness to a certain extent when applied under pressure or can return to their original shape after removal of the load.

In addition, it is advantageous if the carrier foam layer 8 consists of polyolefin (s), polyvinyl chloride or polyurethane. In a particularly preferred embodiment, foamed polyethylenes and / or polypropylenes are used. It is further preferred if the surfaces of the carrier foam layer 8 are physically pretreated, the physical method for the pretreatment in particular being selected from the group corona pretreatment, flame pretreatment or plasma treatment.
Advantageously, alternatively or additionally, the surfaces of the PET film 5 and / or the polyethylene films 10 are physically pretreated.

The physical pretreatment technique commonly referred to as "corona pretreatment" is usually a "dielectric barrier discharge " (DBD) in which high voltage discharges are generated by high frequency AC voltage. In this case, the substrate to be treated is carried out in web form between two high-voltage electrodes, wherein at least one electrode consists of a dielectric material or is coated therewith. The material to be treated is exposed directly to the electrical discharges or at least the reactive gas generated by the discharges. The electrical discharges are often referred to as "corona discharges".

The corona pre-treatment as a method for surface pretreatment of carriers is often used industrially. The process gas is usually the ambient air. The use of process gases other than air, such as nitrogen, carbon dioxide or noble gases, is also known in the art.

Alternatively, the surface of the PSA layer 9 facing the support can be physically pretreated, in particular by corona pretreatment, flame pretreatment or plasma treatment, in order to increase the bond strength between the surface of the PSA PSA layer and the carrier to improve. The physical treatment of the PSA can also be carried out advantageously in air as a process gas, but it can be used as process gases, for example, nitrogen, carbon dioxide or noble gases. For example, nitrogen or a mixture of air and nitrogen have proved to be advantageous.

To increase the bond between the PSA layer 9 and the foamed carrier 8, it has surprisingly been found to be particularly advantageous if both the PSA layer 9 and the foamed carrier 8 on their sides facing each other in the composite, or the corresponding surface of the lower PE Films 10 and the PSA layer 9 are physically pretreated prior to the combination, in particular by one of the aforementioned physical methods. The pretreatment methods of the two layers can be selected independently of each other, preferably they are pretreated by the same method, more preferably by corona pretreatment. By pretreatment of both layers, in particular by means of corona pretreatment, the internal strength of the compound is significantly improved, and the small amount of possibly remaining residues of the adhesive tape when disassembling its substrate (such as a printing cylinder or a printing sleeve) is still possible when using the PSA once noticeably reduced.

In principle, it is now surprising for the person skilled in the art that an increase in the bond strength can be achieved by treating an adhesive surface with a physical method. Since one skilled in the art would expect all of these methods to be accompanied by chain fractures and material degradation, formation of a layer with high content of polar groups but low internal cohesion would be expected. Due to the weakly cohesive layer with increased polarity, better wetting of the substrate by the adhesive is not surprising, but reduced adhesion properties are expected.

The treatment intensity of a corona pretreatment is given as "dose" in [W * min / m ² ], with the dose D = P / (b ^* v), with P = electrical power [W], b = electrode width [m], and v = web speed [m / min].

The corona pretreatment is preferably carried out at a dose of 1 to 150 W * min / m ² . Particularly preferred are for the PSA layer, a dose of 10 to 100 W * min / m ² , in particular a dose of 40 to 60 W * min / m ² . For the foam carrier layer, higher doses are preferably used, so here are a dose of 50 to 150 W * min / m ² and in particular a dose of 80 to 120 W * min / m ² very beneficial. Preferably, the film of polyethylene terephthalate (PET) has a thickness of 5 microns to 500 microns, preferably 5 microns to 60 microns, most preferably 12 microns, 19 microns and 23 microns. In addition to the in FIG. 1a product structure shown, the stabilizing film may also consist of polyolefins, polyurethanes or polyvinyl chloride and be pre-treated in addition to the etching in various ways. Thus, the stabilization films can also be physically and chemically pretreated to improve the anchoring. For physical treatment, the film is preferably treated with flame or corona or plasma. For the chemical pretreatment, the film is provided with primer, wherein in a particularly preferred embodiment, reactive precursors are used. Suitable primer materials are, for example, reactive primers. Furthermore, here as well - alternatively or in addition to the film layer - the adjacent adhesive layers may be pretreated, in particular according to the adhesive layer 9 described above.

In a further preferred embodiment, the stabilizing film of polyethylene terephthalate or another material is printed on one or both sides. This printing can be under a later applied pressure-sensitive adhesive.

For the pressure-sensitive adhesives 7, for example, an acrylate PSA may also be used, but in principle other types of adhesive can also be used.

Furthermore, the adhesive tape can be provided on one or both sides with a cover, in particular one of an anti-adhesive material or anti-adhesive coated material. The paper, for example, or a corresponding film - in particular one or both sides siliconized - be. This ensures a longer storage and convenient handling during use.

But also the other adhesive tape designs, as they are known from the prior art in particular for the bonding of printing plates or printing plates on printing cylinders or sleeves, can be realized according to the invention, wherein in particular by means of the pressure-sensitive adhesive to be used according to the invention at least the adhesive layer for bonding to the cylinder or realized on the sleeve.

Due to its special properties, the double-sided adhesive tape can be used excellently for fixing printing plates, in particular of - in particular multi-layered - photopolymer printing plates (printing plates) on printing cylinders and on printing sleeves (sleeves).

Due to its special design, the adhesive tape, especially with the adhesive forces matched to the printing plate, is excellently suited for bonding the printing plates to the printing cylinders. On the one hand, it is possible to reposition the printing plates before printing, but on the other hand, a firm bonding of the plate is guaranteed during the printing process. Even a paint residue contaminated printing plate can be removed from the pressure-sensitive adhesive tape without any damage. Peeling of the support layer of the plate or the formation of undesirable wrinkles in the plate during removal do not occur. Even after removal of the adhesive tape from the printing cylinder remain no residues.

Printing plates are glued on printing cylinders and on printing sleeves in different ways. Common methods show that FIGS. 2, 3 and 4 :
According to FIG. 2 the cliché (11) by means of an adhesive tape (12) on the printing sleeve (13) or the printing cylinder (13) glued, wherein the adhesive tape (12) is larger than the cliché (11) and therefore with exposed portions (20) below the Cliche (11) sticking out. According to the application variant in FIG. 3 close the edges of the composite of adhesive tape (12) and cliché (11) flush with each other, edge (30).

According to FIG. 4 encloses the adhesive tape (12) for gluing the plate (11) the entire circumference of the printing cylinder (13) and the pressure sleeve (13); the adhesive tape edges abutting the position (40). To lift a composite to prevent, the printing plate (11) is mounted on the tape so that its edges (position 41) are not in place of the tape impact (position 40).

The tapes show a very good assembly behavior. As assembly behavior is understood in the context of this document, in particular the immediate adhesion in the bonding of an adhesive tape by means of the respective pressure-sensitive adhesive layer on a substrate, for a good assembly behavior a short-term pressing with low force so therefore lead to a good and reliable adhesion.

The PSAs to be used according to the invention fulfill the requirements for simple assembly, repositionability, secure hold, in particular also on polar substrates and under the influence of solvents. Furthermore, they are characterized by a simple and residue-free disassembly. They are particularly suitable for use in flexographic printing, as shown above.

Experimental part Test Methods Production of a Haftkiebeyerbundes

A grained cover material with a structured surface siliconized on both sides is coated with a pressure-sensitive adhesive of the examples from solution. This achieves the best possible transfer of the liner structure into the acrylate adhesive.

After drying for 15 minutes at 120 ° C., the coating weight is 35 g / m ² . On the ground side, the coated cover material is laminated with a 19 μm thick PET film etched on both sides by means of trichloroacetic acid. Subsequently, via a transfer carrier, a commercially available acrylate composition with an application rate of 20 g / m ² or an adhesive of similar properties on the uncoated side laminated the etched PET film of the composite and a PE-EVA foam with a thickness of 500 microns and a density of 250 kg / m ³ added.

On this foam carrier, a commercially available acrylate PSA is applied with a mass application of 60 g / m ² on the uncoated side of the previous composite on a transfer support (exposed acrylic adhesive layer).

Gel Permeation Chromatography GPC (Method A) :

The data of the number-average and weight-average molecular weights M _n and M _w and the polydispersity PD in this document relate to the determination by gel permeation chromatography. The determination is carried out on 100 μL of clear filtered sample (sample concentration 4 g / L). The eluent used is tetrahydrofuran with 0.1% by volume of trifluoroacetic acid. The measurement takes place at 25 ° C. The precolumn used is a PSS-SDV column, 5 μm, 10 ³ Å, ID 8.0 mm x 50 mm. For separation, columns of type PSS-SDV, 5 μm, 10 ³ Å and 10 ⁵ Å and 10 ⁶ Å, each having an ID of 8.0 mm × 300 mm are used (columns from Polymer Standards Service, detection by means of a differential refractometer Shodex RI71). , The flow rate is 1.0 mL per minute. The calibration is carried out against PMMA standards (polymethyl methacrylate calibration).

90 ° bond strength test (Method B):

The determination of the bond strength PET is carried out at a test climate of 23 ° C +/- 1 ° C temperature and 50% +/- 5% rel. Humidity.

A 20 mm wide strip of the adhesive tape pattern is applied to a PET plate. This PET plate is previously cleaned twice with isopropanol and then left for 5 minutes in the air, so that the solvent can evaporate.

The pressure-sensitive adhesive strip is pressed onto the substrate ten times with a steel pressure roller with a contact pressure corresponding to a weight of 4 kg and a rolling speed of 1000 mm / min. The adhesive tape is then immediately removed from the substrate at a speed of 300 mm / min and at an angle of 90 °.

The measurement results are given in N / cm and averaged from three measurements.

NC test (method C):

The determination of the bond strength PET is carried out at a test climate of 23 ° C +/- 1 ° C temperature and 50% +/- 5% rel. Humidity.

Two 20 mm wide strips of a 50 μm thick PET film are cleaned twice with ethanol and then left in the air for 5 minutes, so that the solvent can evaporate.

A strip which has been cleaned on both sides only with ethanol marks the blank value. The PET strip is pressed onto the PSA ten times with a steel pressure roller with a contact pressure corresponding to a weight of 4 kg and a rolling speed of 1000 mm / min.

The second strip (NC strip) was drawn through a nitrocellulose (NC) bath (solution 0.1% NC in ethanol) after double purification and dried in the air for 20 minutes. Subsequently, the PET strip is pressed onto the PSA ten times with a steel pressure roller with a contact pressure corresponding to a weight of 4 kg and a rolling speed of 1000 mm / min.

Both samples are stored for 72 hours at 40 ° C. And then for 1 hour at 23 ° C +/- 1 ° C temperature and 50% +/- 5% rel. Air humidity conditioned. The PET strips are peeled off the substrate at a speed of 300 mm / min and at a 90 ° angle to determine the bond strength.

The maximum values of the required force are measured. The measurement results are given in N / cm and averaged from three measurements. The determined value for the bond strength of the NC strip is evaluated in relation to the value of the blank value strip. The change (increase) in bond strength is given as a percentage.

According to the invention, an increase in the bond strength of not more than 15% is advantageous.

Edge lifting (method D): See Fig. 5 Without nitrocellulose (NC)

The determination of the edge lifting takes place at a test climate of 23 ° C +/- 1 ° C temperature and 50% +/- 5% rel. Humidity.

From the double-sided pressure-sensitive adhesive composite (22) to be examined, a 250 mm x 160 mm pattern is cut. This pattern is adhered to a 110 mm diameter steel cylinder (23) with the commercial, exposed, acrylic adhesive layer so that the shorter edges of the patterns are aligned longitudinally of the cylinder. Subsequently, the cover material is peeled off, so that the layer the pressure-sensitive adhesive to be used according to the invention is open. A pressure-sensitive printing plate (21) from DuPont Cyrel HOS having the dimensions of length 210 mm × width 120 mm × thickness 1.7 mm is bonded to the pressure-sensitive adhesive composite pattern bonded in such a way to the PSA to be used according to the invention, that at each edge 20 mm of the underlying pressure-sensitive adhesive composite (centered application on the pressure-sensitive adhesive composite pattern). The cliché is aligned parallel to the upper edge of the pressure-sensitive adhesive composite. Previously, the PET side of the plate was cleaned with isopropanol and allowed to air dry for 5 minutes to allow the solvent to evaporate completely.

Subsequently, the cliché is rolled from the upper cliché edge with a rubber roller (width 100 mm, diameter 30 mm, Shore hardness A 45). The rolling movement takes place in the longitudinal direction of the printing cylinder and is carried out continuously from one longitudinal edge of the plate to the opposite longitudinal edge of the plate and back again. The winding speed is 10 m / min in the transverse direction. The printing cylinder rotates simultaneously with a surface speed of 0.6 m / min, so that describes with the rubber roller relative to the printing plate a zigzag movement in the direction of the second transverse edge of the plate. The assembly of the cliché on the pressure-sensitive adhesive composite was carried out with the appropriate contact force, which is required to fix the cliché over the entire surface and without edge lifting. The steel cylinder is stored with the thus adhered pattern standing for 72 hours at the specified climatic condition (40 ° C).

Due to its restoring behavior, the cliché tends to edge off. Depending on the resistance of the bond of the PSA to be used according to the invention to the printing plate, detachment of the cliché edges which run in the longitudinal direction of the steel cylinder is evident. To assess this behavior, the length L of the lifted cliché edge is determined up to the first remaining contact point with the substrate (determination of the maximum value of the lift of each cliché edge, mean value from the evaluation of both edges and three measurement runs).

Advantageously according to the invention is a Kantenabheben of a maximum of 5mm.

With nitrocellulose (NC)

To assess the resistance of the adhesive to influences of the binders in printing inks, a 0.1% solution of cellulose nitrate in ethanol is prepared. The test uses the low-viscosity "Walsroder® Nitrocellulose" A400, which has a nitrogen content of 10.7% - 11.3% and a degree of substitution of 1.89 - 2.05.

The cliché with the dimensions length 210 mm x width 120 mm x thickness 1.7 mm is cleaned with isopropanol and left for 5 min in air, so that the solvent can evaporate completely. The cliché is coated with 3 ml of the NC solution (0.1% NC and 99.9% ethanol) using a piece of pulp measuring 30 mm long x 30 mm wide x 2 mm thick. This is done in strips initially horizontally. It is important to ensure that the cliché has been wetted with the solution over its entire surface. The cliché is spread with the same piece of pulp a second time, this time in a vertical direction.

Subsequently, the plate is left for 1 minute in the air, so that the solvent can evaporate. The cliché is now glued, stored and evaluated analogously to a cliché without NC.

Advantageously according to the invention is a Kantenabheben of a maximum of 5mm.

Dismantling (method E): Without nitrocelluslose (NC)

The determination of the edge lifting takes place at a test climate of 23 ° C +/- 1 ° C temperature and 50% +/- 5% rel. Humidity.

From the double-sided pressure-sensitive adhesive composite to be examined, a 480 mm x 340 mm pattern is cut. This pattern is adhered to a 110 mm diameter steel cylinder with the exposed acrylic pressure-sensitive layer so that the longer edges of the patterns are aligned longitudinally of the cylinder. Subsequently, the covering material is peeled off so that the layer of the PSA to be used according to the invention is exposed. On the so-bonded pressure-sensitive adhesive composite samples is a full-surface exposed printing plate from. DuPont Cyrel HOS with the dimension length 420 mm x width 330 mm x thickness 1.14 mm so on the invention to be used

Adhesive adhesive glued that at the vertical cliché edges each 20 mm of the underlying pressure-sensitive adhesive composite survive (centered application on the pressure-sensitive adhesive composite pattern). The cliché is aligned so that the cliché center is placed over the gap of the double-sided pressure-sensitive adhesive bond.

Previously, the PET side of the plate was cleaned with isopropanol and allowed to air dry for 5 minutes to allow the solvent to evaporate completely. Subsequently, the cliché is rolled from the upper cliché edge with a rubber roller (width 100 mm, diameter 30 mm, Shore hardness A 45). The rolling movement takes place in the longitudinal direction of the printing cylinder and is carried out continuously from one longitudinal edge of the plate to the opposite longitudinal edge of the plate and back again. The winding speed is 10 m / min in the transverse direction. The impression cylinder simultaneously rotates at a surface velocity of 0.6 m / min, so that describes with the rubber roller relative to the printing plate a zigzag movement in the direction of the second transverse edge of the cliché. The assembly of the cliché on the pressure-sensitive adhesive composite was carried out with the appropriate contact force, which is required to fix the cliché over the entire surface and without edge lifting. The steel cylinder is stored with the thus glued pattern perpendicular to one of its front sides standing for 72 hours at 40 ° C.

With nitrocellulose (NC)

A cliche of dimension length 420 mm x width 330 mm x thickness 1.14 mm is cleaned on the PET side with isopropanol and allowed to air dry for 5 minutes so that the solvent can completely evaporate. The cliché is coated with 5 ml of the NC solution (0.1% NC and 99.9% ethanol) using a piece of pulp measuring 30 mm x 30 mm x 4 mm thick. This is done in strips initially horizontally. It is important to ensure that the cliché has been wetted with the solution over its entire surface. The cliché is spread with the same piece of pulp a second time, this time in a vertical direction.

Subsequently, the plate is left for 1 minute in the air, so that the solvent can evaporate. The cliché is now glued analogous to a cliché for assessing the demounting and stored for 72 hours at 40 ° C.

The subjectively required force required for dismantling both clichés is assessed. The disassembly is carried out while standing, feet shoulder width apart. The cliché is gripped with both hands on an edge running to the longitudinal direction of the steel cylinder and withdrawn (radial) at about 300 mm / min in the transverse direction to the steel cylinder.

The division of effort describes the evaluation scheme used in the industry.

A force marked "+" will be considered acceptable by those skilled in the art. Negative ratings ("-") are considered unacceptable for daily use.

Micro shear test (method F)

This test serves to quickly test the shear strength of adhesive tapes under temperature load.

Sample preparation for micro-shear test:

An adhesive tape cut from the respective sample sample (length approx. 50 mm, width 10 mm) is glued onto a steel test plate cleaned with acetone, so that the steel plate the adhesive tape projects right and left and that the adhesive tape projects beyond the test panel by 2 mm at the upper edge. The bond area of the sample is height x width = 13 mm x 10 mm. The bonding site is then overrolled six times with a 2 kg steel roller at a speed of 10 m / min. The tape is reinforced flush with a sturdy tape that serves as a support for the distance sensor. The sample is suspended vertically by means of the test plate.

Micro Test:

The sample to be measured is loaded at the lower end with a weight of 300 g. The test temperature is 40 ° C, the test duration 30 minutes (15 minutes load and 15 minutes unloading). The shear distance after the specified test duration at constant temperature is given as the result in μm, as the maximum value ["max"; maximum shearing distance due to 15-minute load]; as minimum value ["min"; Shearing distance ("residual deflection") 15 min after discharge; Relief is followed by a return movement through relaxation]. Also indicated is the elastic fraction in percent ["elast"; elastic proportion = (max - min) · 100 / max].

Examples chemicals:

crosslinkers: Al chelate: Al (III) acetylacetonate Company Sigma Aldrich Nitrocellulose (NC): Walsroder® Nitrocellulose A400

Unless otherwise specified, all percentages below are by weight.

Amounts of the composition of the adhesive of the polyamercomponent I, the optionally present polymer component II are based on 100% by weight of the total compound composed by these components. Quantities of the crosslinker are given in parts by weight (GT), based in each case on 100 parts by weight of all polyacrylate components.

example 1 Preparation of polyacrylate I (PA I)

A conventional 300 L reactor for free-radical polymerizations was charged with 2.0 kg of acrylic acid, 30.0 kg of isobornyl acrylate (BA), 68.0 kg of 2-ethylhexyl acrylate (EHA) and 72.4 kg of gasoline / acetone (70:30) , After passing nitrogen gas through with stirring for 45 minutes, the reactor was heated to 58 ° C and 50 g of Vazo® 67 was added. Subsequently, the jacket temperature was heated to 75 ° C and the reaction was carried out constantly at this outside temperature. After 1 h of reaction time, 50 g of Vazo® 67 were added again. After 3 hours, it was diluted with 20 kg of gasoline / acetone (70:30) and after 6 hours with 10.0 kg of gasoline / acetone (70:30). To reduce the residual initiators, 0.15 kg of Perkadox® 16 were added after 5.5 and after 7 hours. The reaction was stopped after 24 h reaction time and cooled to room temperature. Molecular masses by GPC (measurement method A): M _n = 62,800 g / mol; M _w = 852,600 g / mol.

Hansen solubility parameter: δ _d = 17.1, δ _p = 6.5 and δ _H = 4.9

Example 2 Preparation of polyacrylate II (PA II)

A conventional 2 L glass reactor suitable for radical polymerizations under boiling-cooling was charged with 300 g of a monomer mixture containing 219 g of ethylhexyl acrylate, 60 g of methyl acrylate and 21 g of acrylic acid and 200 g of acetone: 60/95 (1: 1). After passing nitrogen gas through with stirring for 45 minutes, the reactor was heated to 58 ° C. and 0.15 g of 2,2'-azodi (2-methylbutyronitrile (Vazo 67®, DuPont) dissolved in 6 g of acetone were added The external heating bath was heated to 75 ° C. and the reaction was carried out constantly at this external temperature After 1 h of reaction time, 0.15 g of VAZO 67® dissolved in 6 g of acetone was again added. 95 diluted.

After a reaction time of 5:30 hours, 0.45 g of bis (4-tert-butylcyclohexanyl) peroxy-dicarbonate (Perkadox 16®, Akzo Nobel) dissolved in 9 g of acetone was added. After 7 hours reaction time, another 0.45 g of bis (4-tert-butylcyclohexanyl) peroxy-dicarbonate (Perkadox 16®, Akzo Nobel) dissolved in 9 g of acetone was added. After 10 hours of reaction time was diluted with 90 g of low-boiling point spirit 60/95. The reaction was stopped after 24 h reaction time and cooled to room temperature.

Molecular masses by GPC (measurement method A): Mn = 52500 g / mol, M _W = 626000 g / mol) Hansen solubility parameter: δ _d = 17.0 δ _p = 8.0 and δ _H = 6.5

Example 3 Preparation of the polyacrylate III (PA III)

A conventional 2 L glass reactor suitable for free-radical polymerizations with evaporative cooling was charged with 300 g of a monomer mixture containing 130.5 g of butyl acrylate, 130.5 g of ethylhexyl acrylate, 30 g of methyl acrylate and 15 g of acrylic acid, and 200 g of acetone: 60/95 petroleum spirit (1 : 1) filled. After passing nitrogen gas through with stirring for 45 minutes, the reactor was heated to 58 ° C. and 0.15 g of 2,2'-azodi (2-methylbutyronitrile (Vazo 67®, DuPont) dissolved in 6 g of acetone were added The external heating bath was heated to 75 ° C. and the reaction was carried out constantly at this external temperature After 1 h of reaction time, 0.15 g of VAZO 67® dissolved in 6 g of acetone was again added. 95 diluted.

After a reaction time of 5:30 hours, 0.45 g of bis (4-tert-butylcyclohexanyl) peroxy-dicarbonate (Perkadox 16®, Akzo Nobel) dissolved in 9 g of acetone was added. After 7 hours reaction time, another 0.45 g of bis (4-tert-butylcyclohexanyl) peroxy-dicarbonate (Perkadox 16®, Akzo Nobel) dissolved in 9 g of acetone was added. After 10 hours of reaction time was diluted with 90 g of low-boiling point spirit 60/95. The reaction was stopped after 24 h reaction time and cooled to room temperature.

Molar masses by GPC (measurement method A): Mn = 98500 g / mol, M _W = 1515000 g / mol). Hansen solubility parameter: δ _d = 17.0 δ _p = 8.2 and δ _H = 6.4

Example 4 Preparation of polyacrylate IV (PA IV)

A conventional 2 L glass reactor suitable for free-radical polymerizations under evaporative cooling was charged with 300 g of a monomer mixture containing 291 g of ethylhexyl acrylate, 9 g of acrylic acid and 200 g of acetone: 60/95 (1: 1). After passing nitrogen gas through with stirring for 45 minutes, the reactor was heated to 58 ° C. and 0.15 g of 2,2'-azodi (2-methylbutyronitrile (Vazo 67®, DuPont) dissolved in 6 g of acetone were added The external heating bath was heated to 75 ° C. and the reaction was carried out constantly at this external temperature After 1 h of reaction time, 0.15 g of VAZO 67® dissolved in 6 g of acetone was again added. 95 diluted.

After a reaction time of 5:30 hours, 0.45 g of bis (4-tert-butylcyclohexanyl) peroxy-dicarbonate (Perkadox 16®, Akzo Nobel) dissolved in 9 g of acetone was added. After 7 hours reaction time, another 0.45 g of bis (4-tert-butylcyclohexanyl) peroxy-dicarbonate (Perkadox 16®, Akzo Nobel) dissolved in 9 g of acetone. After 10 hours of reaction time was diluted with 90 g of low-boiling point spirit 60/95. The reaction was stopped after 24 h reaction time and cooled to room temperature. Molar masses by GPC (measurement method A): Mn = 56500 g / mol, M _W = 1037000 g / mol). Hansen solubility parameter: δ _d = 16.8 δ _p = 7.1 and δ _H = 5.2

Example 5 Preparation of polyacrylate V (PA V)

A conventional 2 L glass reactor suitable for free-radical polymerizations with evaporative cooling was charged with 300 g of a monomer mixture containing 130.5 g of butyl acrylate, 130.5 g of ethylhexyl acrylate, 30 g of methyl acrylate and 15 g of acrylic acid and 200 g of acetone: petroleum spirit 60/95 (30 : 70). After passing nitrogen gas through with stirring for 45 minutes, the reactor was heated to 58 ° C. and 0.15 g of 2,2'-azodi (2-methylbutyronitrile (Vazo 67®, DuPont) dissolved in 6 g of acetone were added The external heating bath was heated to 75 ° C. and the reaction was carried out constantly at this external temperature After 1 h of reaction time, 0.15 g of VAZO 67® dissolved in 6 g of acetone was again added. 95 diluted.

After a reaction time of 5:30 hours, 0.45 g of bis (4-tert-butylcyclohexanyl) peroxy-dicarbonate (Perkadox 16®, Akzo Nobel) dissolved in 9 g of acetone was added. After 7 hours reaction time, another 0.45 g of bis (4-tert-butylcyclohexanyl) peroxy-dicarbonate (Perkadox 16®, Akzo Nobel) dissolved in 9 g of acetone was added. After 10 hours of reaction time was diluted with 90 g of low-boiling point spirit 60/95. The reaction was stopped after 24 h reaction time and cooled to room temperature.

Molar masses by GPC (measurement method A): Mn = 43500 g / mol, M _W = 730000 g / mol). Hansen solubility parameter: δ _d = 16.8 δ _p = 7.1 and δ _H = 5.1

Example 6 Preparation of the polyacrylate VI (PA VI)

A conventional 2 L glass reactor suitable for free-radical polymerizations with evaporative cooling was charged with 300 g of a monomer mixture containing 228 g of ethylhexyl acrylate, 60 g of stearyl acrylate and 12 g of acrylic acid and 200 g of acetone: petroleum spirit 60/95 (1: 1). After passing nitrogen gas through with stirring for 45 minutes, the reactor was heated to 58 ° C. and 0.15 g of 2,2'-azodi (2-methylbutyronitrile (Vazo 67®, DuPont) dissolved in 6 g of acetone were added the external heating bath was at 75 ° C heated and the reaction is carried out constantly at this outside temperature. After 1 h of reaction time again 0.15 g of VAZO 67®, dissolved in 6 g of acetone, was added. After 3 hours was diluted with 90 g of low-boiling point spirit 60/95.

After a reaction time of 5:30 hours, 0.45 g of bis (4-tert-butylcyclohexanyl) peroxy-dicarbonate (Perkadox 16®, Akzo Nobel) dissolved in 9 g of acetone was added. After 7 hours reaction time, another 0.45 g of bis (4-tert-butylcyclohexanyl) peroxy-dicarbonate (Perkadox 16®, Akzo Nobel) dissolved in 9 g of acetone was added. After 10 hours of reaction time was diluted with 90 g of low-boiling point spirit 60/95. The reaction was stopped after 24 h reaction time and cooled to room temperature.

Molecular weight by GPC (measurement method A): Mn = 77900 g / mol, M _W = 1334000 g / mol) Hansen solubility parameter: δ _d = 16.8 δ _p = 6.6 and δ _H = 4.8

Example 7

The PA I, prepared analogously to Example 1, was treated with a crosslinker solution (3% by weight in acetone) and coated as described in " Preparation of a pressure-sensitive adhesive composite ". The corresponding adhesive tape pattern was conditioned for one week under standard conditions (23 ° C., 50% relative humidity).

The polymer component PA I was crosslinked with Al chelate (0.3 parts by weight (GT) based on 100 parts by weight polymer component 1).

Examples 8-27

The PA I (polymer component 1), prepared analogously to Example 1, was added with stirring with a second polymer component. The polymer component 2 and the respective amounts are shown in Table 1. Subsequently, the polymer mixture was admixed with a crosslinker solution (3% by weight in acetone) and coated as described in " Preparation of a pressure-sensitive adhesive composite" . The corresponding adhesive tape pattern was conditioned for one week under standard conditions (23 ° C., 50% relative humidity).

The polymer mixture was crosslinked with Al chelate (0.3 pbw based on 100 pbw polymer component 1 + polymer component 2). Table 1 example Polmerkompenente 1 Proportion of polymer components 1 [% by weight] Polmerkompenente 2 Proportion of polymer components 2 [% by weight] GT crosslinker (Al-chelate) 8th PA I (example 1) 98 PA II (example 2) 2 0.3 9 PA I (example 1) 95 PA II (example 2) 5 0.3 10 PA I (example 1) 90 PA II (example 2) 10 0.3 11 PA I (example 1) 85 PA II (example 2) 15 0.3 12 PA I (example 1) 98 PA III (example 3) 2 0.3 13 PA I (example 1) 95 PA III (example 3) 5 0.3 14 PA I (example 1) 90 PA III (example 3) 10 0.3 15 PA I (example 1) 85 PA III (example 3) 15 0.3 16 PA I (example 1) 98 PA IV (Example 4) 2 0.3 17 PA I (example 1) 95 PA IV (Example 4) 5 0.3 18 PA I (example 1) 90 PA IV (Example 4) 10 0.3 19 PA I (example 1) 85 PA IV (Example 4) 15 0.3 20 PA I (example 1) 98 PA V (example 5) 2 0.3 21 PA I (example 1) 95 PA V (example 5) 5 0.3 22 PA I (example 1) 90 PA V (example 5) 10 0.3 23 PA I (example 1) 85 PA V (example 5) 15 0.3 24 PA I (example 1) 98 PA VI (example 6) 2 0.3 25 PA I (example 1) 95 PA VI (example 6) 5 0.3 26 PA I (example 1) 90 PA VI (example 6) 10 0.3 27 PA I (example 1) 85 PA VI (example 6) 15 0.3

Results Examples of the Invention: 8-10, 12-14, 16-18

Counterexamples (do not meet the requirements of the invention): 7, 11, 15, 19-27.

The results of the tests are shown in Table 2.

All adhesives according to the invention also have a crosslinking state which, according to method F, corresponds to a micro-shear path between 125 μm and 250 μm. Polyacrylate PSAs consist in the known prior art of only one polymer component. As Example 7 shows, can be achieved with a polyacrylate basically a pressure sensitive adhesive with good adhesion to PET (Method F) and advantageous edge lifting (Method D) with good disassembly (Method E, without cellulose nitrate [short NC)]. Significant weaknesses occur in such a pressure-sensitive adhesive, however, when using the corresponding adhesive tapes in printing processes with cellulose nitrate-containing printing inks. Example 7 shows an increase in adhesion due to NC of 51.3% (Method C), and at the same time a non-advantageous disassembly behavior.

Without this being foreseen, the object according to the invention is achieved by an adhesive which contains at least two polymer components.

By investigations by means of Dynamic Differential Scanning Calorimetry (DSC) and / or, if advantageous for the corresponding sample, electron screen investigation, it was found that all PSAs according to the invention were phase-separated, whereas all compositions with a difference Z less than 1 (Examples 20 to 27) did not.

The polymer components are preferably chosen such that the difference Z of the polymer components assumes at least the value 1.

It can be seen from the results of Examples 20-27 that a pressure-sensitive adhesive consisting of 2 polymer components with a difference Z of less than 1 can not solve the stated problem. In the examples mentioned, an increase in the bond strength by cellulose nitrate (NC) of at least 20% can be determined (Method C). This non-advantageous property is also reflected in a disadvantageous disassembly (method E).

Surprisingly for a person skilled in the art, pressure-sensitive adhesives consisting of 2 polymer components having a difference Z greater than 1 show no disadvantageous behavior on contact with NC in adhesive tests. Examples 8-19 demonstrate this by showing an increase in adhesive strength by NC (Method C) of only a maximum of 14.6%. In addition, in application test for disassembly (method E) only advantageous results can be determined. In addition, the bond strength to PET according to Method B is not influenced in comparison to the results of Example 7. By contrast, in Examples 8-19, a non-advantageous trend of edge lifting by Method D can be seen. An unacceptable edge lift of> 5 mm occurs at a level of 15% by weight of the second polymer component. Examples 11, 15, 19 show these results, although they also show this phase separation (DSC or electron microscopy).

Thus, according to the invention, examples 8-10, 12-14, 16-18 are to be emphasized with regard to advantageous edge lifting of a maximum of 5 mm (method E), easy disassembly according to method D and advantageously low increase in adhesive force by NC (method C). Table 2 example Compenents 1 Wt .-% Compenents 2 Wt .-% Z Adhesive force PET [N / cm] (method B) MSW (Method F) NC test (method C) application test max [μm] elast PET strip Adhesive force [N / cm] Increase of bond strength by NC [%] plate Edge lifting (method D) Dismantling (method E) 7 PA I 100 / / / 6.0 79 80 without NC 3.9 51.3 without NC 1 + with NC 5.9 with NC 0 - 8th PA I 98 PA II 2 3.21 5.9 73 72 without NC 3.5 8.6 without NC 1 + with NC 3.8 with NC 1 + 9 PA I 95 PA II 5 3.21 6.1 71 73 without NC 3.3 9.1 without NC 1 + with NC 3.6 with NC 1 + 10 PA I 90 PA II 10 3.21 5.7 75 81 without NC 3.6 5.6 without NC 3 + with NC 3.8 with NC 2 + 11 PA I 85 PA II 15 3.21 5.7 78 80 without NC 4.0 5.0 without NC 7 + with NC 4.2 with NC 6 + 12 PA I 98 PA III 2 3.42 6.2 76 73 without NC 3.5 5.7 without NC 1 + with NC 3.7 with NC 1 + 13 PA I 95 PA III 5 3.42 6 70 70 without NC 3.3 3.0 without NC 1 + with NC 3.4 with NC 1 + 14 PA I 90 PA III 10 3.42 5.8 71 76 without NC 3.5 0.0 without NC 3 + with NC 3.5 with NC 3 + 15 PA I 85 PA III 15 3.42 5.9 74 83 without NC 3.3 6.1 without NC 9 + with NC 3.5 with NC 7 + 16 PA I 98 PA IV 2 1.14 5.6 74 83 without NC 4.1 14.6 without NC 1 + with NC 4.7 with NC 0 + 17 PA I 95 PA IV 5 1.14 5.8 66 84 without NC 3.7 13.5 without NC 1 + with NC 4.2 with NC 1 + 18 PA I 90 PA IV 10 1.14 5.9 77 84 without NC 4 10.0 without NC 5 + with NC 4.4 with NC 5 + 19 PA I 85 PA IV 15 1.14 6.3 77 84 without NC 3.8 10.5 without NC 7 + with NC 4.2 with NC 6 + 20 PA I 98 PA V 2 0.98 5.6 65 73 without NC 3.8 26.3 without NC 1 + with NC 4.8 with NC 0 - 21 PA I 95 PA V 5 0.98 6.3 70 71 without NC 3.8 21.1 without NC 1 + with NC 4.6 with NC 1 - 22 PA I 90 PA V 10 0.98 6.2 71 78 without NC 3.7 24.3 without NC 5 + with NC 4.6 with NC 0 - 23 PA I 85 PA V 15 0.98 5.9 79 80 without NC 3.5 20.0 without NC 8th + with NC 4.2 with NC 1 - 24 PA I 98 PA VI 2 0.44 6.2 71 80 without NC 4.1 43.9 without NC 1 + with NC 5.9 with NC 1 - 25 PA I 95 PA VI 5 0.44 6.0 67 73 without NC 4.4 40.9 without NC 1 + with NC 6.2 with NC 0 - 26 PA I 90 PA VI 10 0.44 5.6 79 84 without NC 3.9 48.7 without NC 4 + with NC 5.8 with NC 1 - 27 PA I 85 PA VI 15 0.44 5.9 77 73 without NC 3.5 57.1 without NC 7 + with NC 5.5 with NC 1 - HSP (Stefanis-Panayiotou) CAS monomer δ _d δ _p δ _h 79-10-7 Acrylic acid 17.7 8.6 11.1 141-32-2 n-butyl acrylates 17.1 8.6 6.5 28343-58-0 Heptadecyl acrylate 15.0 1.6 2.5 689-12-3 Isobutyl acrylate 16.9 8.2 6.6 12542-30-2 Dihydrodicyclopentadienyl acrylates 20.2 4.6 4.0 140-88-5 Ethyl acrylates 17.1 9.2 7.3 7328-17-8 Ethylene diglycol acrylate 17.2 10.4 6.2 103-11-7 2-ethylhexyl acrylate 16.7 7.0 4.7 2499-95-8 Hexyl acrylates 17.0 7.9 5.7 818-61-1 Hydroxyethyl acrylates 17.8 12.0 15.3 5888-33-5 Isobornyl acrylate 17.6 6.1 4.1 29590-42-9 Isooctyl acrylate 16.8 7.0 5.0 2156-97-0 Lauryl acrylate 16.9 2.5 0.8 96-33-3 Methyl acrylates 17.2 9.5 7.7 3121-61-7 Methoxyethyl acrylates 17.5 10.7 7.8 925-60-0 Propyl acrylates 17.1 8.9 6.9 149021-58-9 propylheptyl 16.7 6.4 3.9 4813-57-4 Stearyl acrylates 16.7 1.7 0.1 1663-39-4 tert-butyl acrylates 16.4 9.5 6.0 97-88-1 n-butyl methacrylate 16.7 8.4 6.0 6140-75-6 Heptadecyl meth acrylate 14.6 2.3 2.8 101-43-9 Cyclohexyl methacrylate 17.9 6.4 5.8 688-84-6 2-Ethyhexyl methacrylate 16.4 6.8 4.2 97-63-2 Ethyl methacrylate 16.8 9.0 6.8 00106-91-2 Glycidyl methacrylate 18.6 12.0 7.6 868-77-9 Hydroxyethyl methacrylates 17.4 11.5 14.4 97-86-9 Iso-butyl methacrylate 16.5 8.0 6.2 7534-94-3 Isobornyl methacrylate 17.3 5.9 3.6 142-90-5 Lauryl methacrylate 16.5 3.3 1.0 80-62-6 Methyl methacrylates 16.8 9.3 7.2 32360-05-7 Stearyl methacrylate 16.4 2.5 0.3 84100-23-2 tert-butyl cyclohexyl methacrylate 15.6 3.6 3.3 585-07-9 tert-butyl methacrylate 16.1 9.3 5.5 98-83-9 alpha-methyl styrene 18.6 3.4 2.5 107-13-1 Acrylonitrile 18.0 14.2 6.7 107-58-4 N-tert-butyl acrylamide 14.6 11.3 5.9 2235-00-9 N-vinyl caprolactam 20.2 10,8 6.4 88-12-0 N-vinylpyrrolidone 20.2 11.5 7.2 100-42-5 Styrene 18.9 2.6 2.2 108-05-4 vinyl acetates 16.7 9.5 8.0 79-06-1 acrylamides 16.2 11.4 11.9

Claims (13)

1. Use of a pressure-sensitive adhesive comprising at least 60 wt% of a polymer blend,
   where the polymer blend consists of a first polymer component A, a second polymer component B, and optionally one or more further polymer components, where the first polymer component A is present at not less than x wt% in the polymer blend, where 90 ≤ x ≤ 99,
   and where the second polymer component B and any further polymer components present are present in total at y wt% in the polymer blend, where y = 100 - x,
   where each polymer component derives to an extent of at least 60 wt% from (meth)acrylic monomers, characterized in that none of the polymer components is homogeneously miscible at room temperature with any of the other polymer components, and so a multiphase system is present, for bonding printing plates to surfaces, more particularly to curved surfaces.
2. Use according to Claim 1, characterized in that the polymer blend makes up at least 99.9 wt% of the pressure-sensitive adhesive, more particularly 100% of the pressure-sensitive adhesive.
3. Use according to either of the preceding claims, characterized in that the first polymer component A consists of a single polymer.
4. Use according to either of Claims 1 and 2, characterized in that the polymer component A is a homogeneous mixture of two or more polymers.
5. Use according to any of the preceding claims, characterized in that the polymer blend is formed exclusively of polymer components A and B, and so a two-phase system is present.
6. Use according to any of the preceding claims, characterized in that the polymer component B consists of a single polymer.
7. Use according to any of Claims 1 to 5, characterized in that the polymer component B is a homogeneous mixture of two or more polymers.
8. Use according to Claim 1, characterized in that each polymer component comprises polymers obtained in each case by polymerization of monomers, the composition of the monomers for the polymers of each polymer component being selected such that the dissimilarity Z of the Hansen solubility parameters of each of the polymer components with each of the other polymer components adopts a value of more than 1, the Hansen solubility parameter being determined by the method specified in the descritpion.
9. Use according to either of Claims 1 and 8, characterized in that the pressure-sensitive adhesive is crosslinked.
10. Use according to any of Claims 1 to 9, characterized in that the printing plate is one composed of a polyethylene terephthalate film bearing at least one applied layer of a photopolymer.
11. Use according to any of Claims 1 to 10, characterized in that the surface to which the printing plate is bonded consists of steel, polyurethane or of a glass fibre-resin material.
12. Use according to any of Claims 1 to 11, characterized in that the surface to which the printing plate is bonded is part of a printing cylinder or printing sleeve.
13. Use according to any of Claims 1 to 12 in printing processes using printing inks containing cellulose nitrate.

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